With the more fuels mod, or some mods that change the property of a matter i get an error that says "bad argument #2 to 'set_property' (number expected, got string). Please help.
It looks like a bug in TPT. I just fixed it, so it should be fixed whenever 94.2 comes out. (Which may be in a month or so, no concrete plans on a date right now)
For now, don't use the element that causes it. It's likely that that element has been broken for years.